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Project: Transformer Checker

Discussion in 'Electronic Projects' started by hsab, Mar 23, 2005.

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  1. Cool_buddy_57

    Cool_buddy_57 New Member

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    Yes i like it but.
    What is the neon bulb?

    A neon bulb mean LED or any thing else
     
  2. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It means a 'neon bulb', it's a very common old component, they require a high voltage (about 70V to 90V to strike) - nothing else will do. If you really can't find one, try old switched mains sockets, those that have a red/orange light, they use a neon bulb.
     
  3. philba

    philba New Member

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    maybe this is a dumb question but how often do transformers fail with a short inside the coils? I guess if they really got cooked and melted the insulation on the wires it could happen but wouldn't that be pretty obvious from a visual inspection?
     
  4. dave

    Dave New Member

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  5. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It's a common failure mode, particularly in line output transformers, but also in modern cheap mains transformers - however, modern transformers usually have internal (non-replaceable) heat fuses, and the heat generated by the shorted turn will usually blow the heat fuse.
     
  6. Cool_buddy_57

    Cool_buddy_57 New Member

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    Ok Dear u say Right
    But u say that neon bulb require 70V to 90V to stike. And in transformer checker circuit 6V battery is used. What u saying about this?:D
     
  7. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    That's the entire point behind the project!, when the current is discontinued a high back EMF is generated, it's that high voltage that causes the neon to strike. If there's a shorted turn in the transformer this will damp the back EMF, and the neon won't light.
     
  8. jkr6211

    jkr6211 New Member

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    very ingenius method
     
  9. Speakerguy

    Speakerguy Active Member

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    The transformer will easily create a high voltage pulse and light the LED/neon bulb when you release the switch.

    I had a transformer with a 1mH coil that I was switching with a MOSFET (ignition coil primary) that was being charged with 12V. The voltage spike at the drain of the low-side-switch n-channel mosfet was >200V.
     
    Last edited: Jun 11, 2008
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